Ventricular Flow Field Visualization During Mechanical Circulatory Support in the Assisted Isolated Beating Heart.

Investigations of ventricular flow patterns during mechanical circulatory support are limited to in vitro flow models or in silico simulations, which cannot fully replicate the complex anatomy and contraction of the heart. Therefore, the feasibility of using echocardiographic particle image velocimetry (Echo-PIV) was evaluated in an isolated working heart setup. Porcine hearts were connected to an isolated, working heart setup and a left ventricular assist device (LVAD) was implanted. During different levels of LVAD support (unsupported, partial support, full support), microbubbles were injected and echocardiographic images were acquired. Iterative PIV algorithms were applied to calculate flow fields. The isolated heart setup allowed different hemodynamic situations. In the unsupported heart, diastolic intra-ventricular blood flow was redirected at the heart's apex towards the left ventricular outflow tract (LVOT). With increasing pump speed, large vortex formation was suppressed, and blood flow from the mitral valve directly entered the pump cannula. The maximum velocities in the LVOT were significantly reduced with increasing support. For the first time, cardiac blood flow patterns during LVAD support were visualized and quantified in an ex vivo model using Echo-PIV. The results reveal potential regions of stagnation in the LVOT and, in future the methods might be also used in clinical routine to evaluate intraventricular flow fields during LVAD support.

Paediatric ventricular assist devices: current achievements.

In chronic cardiomyopathy, mechanical circulatory support plays an increasingly important role for children as the shortage of suitable donor hearts increases times on the transplant waiting list. Ventricular assist devices (VADs) for adults have evolved dramatically over the last decade, both as a bridge to transplantation and for permanent support. In contrast, VADs designed for children, especially for all age groups, are still in their infancy. The Medos HIA and the Berlin Heart Excor are specially designed for children with a body surface area <1.2 m2. Increased experience with existing paediatric VADs and the introduction of third-generation VADs for the paediatric age group offer new possibilities for children suffering from end-stage heart failure. We review the literature on this topic, summarise the indications and contraindications for long-term support VADs and describe the decision-making algorithm used at our institution for use of long-term VADs in children.